Sound track for multilayer film



Jan. 10, 1939. l.. D. MANNES ET AL M3778? SOUND TRACK FOR MULTILAYERFILM Filed Dec, ll, 1935 FHM +22 15 Z;

BLEACH, \\\QQ REEXPSE fvD DEVELOP SULF/IRE ATTORNEYS Patented Jan. 10,1939 UNITED STATES PATENT OFFICE SOUND TRACK FOR MULTILAYER FILM NewJersey Application December 11, 1936, Serial No. 115,404

2 Claims. (Cl. 535-2) This invention relates to sound tracks inphotographic film and particularly to a method for producing a soundtrack in multi-layer film in which colored images are produced.

Our prior application, Serial No. 8,516, filed February 27, 1935,describes a method for producing natural colored images in photographicfilm having three differentially sensitized layers on one side of asupport. According to the method described in our prior application thefilm is exposed to the object to be recorded and is then developed in anordinary developer. The silver image is then removed by a suitablesolvent. If a reversed image is to be formed or if a negative is desiredthe film is fixed to remove undeveloped silver halide and the remainingsilver bleached tion which destroys the color images in the upper layersand again forms a developable salt in these layers. The upper layers arethen again del veloped to form colored images and the upper or outermostlayer again bleached and recolored to form a third colored image.

In the preferred form of the process described in our prior applicationthe lowermost layer of the final film carries a minus red image, themiddle layer carries a minus green image and the upper or outer layercarries a minus blue image. Of these three images the minus red image isthe only one of the three which is at all suitable for the formation ofa sound track, on account of its high degree of absorption of red light.This minus red image is on the bottom or inner emulsion layer and if thesound track is recorded or printed from the outer surface the passage ofthe light through the upper two emulsion layers decreases the resolvingpower of the lower layer image considerably below the required limit.The sound image might be recorded through the film support but thiswould require local or total removal of the backing with consequentdanger of halation and the added problem of noise due to the recordingof scratches on the film base. In our prior application we also proposedrecordlng the sound image in all three emulsion layers.

Here too, however, there is a lowering of the resolving power of theimage.

It is, therefore, an object of the present invention to provide animproved sound track in photographic film having three superposeddifferentially sensitized layers used for color photography. A furtherobject is to provide a sound track which will not be affected bysubsequent bleaching and color development steps of the multi-layerfilm. A still further object is to provide a. sound track in multi-layerfilm having a high resolving power.

As the upper emulsion layer of the multi-layer film described in ourprior application, Serial No. 8,516 has a high resolving power, which isfurther increased, for blue light, by the presence of a yellow filterdye, this layer is well vsuited to the requirements of a sound track.However, the minus blue dye image remaining in this layer afterdevelopment is virtually useless as it is nearly transparent to thephoto-electric cell used in sound reproducing. It is, therefore,proposed to utilize the silver image in the top layer before it isfinally removed by converting it to silver sulfide in the sound trackarea.

In the accompanying drawing Fig.`1 is a diagrammatic view of theapparatus used in the formation of a silver sulfide sound track;

Fig. 2 is a flow sheet showing the steps in the formation of the soundtrack; and

Fig. 3 is a. plan view showing the method ofl applying treatingsolutions to the sound track area of the film.

For a negative-positive process the sound track record can be confinedto the top layer by recording or printing through a blue filter. For areversal process the sound track may be confined to the surface layer byone of two methods. The first method is to record through a blue filterand fully flash the sound track through a yellow filter, thus clearingout the lower two layers, which are sensitive to red and green light, byreversal. This leaves the image in the upper layer only. The secondmethod which is particularly applicable to direct camera recording is touse a lamp operated at suiciently low color temperature to give apredominantly yellow-orange light. An exposure which is sufficient toproduce a correct sound image by blue light in the upper layer will thenautomatically over-expose the records in the lower two layers to give arelatively low density in these layers after reversal.

A conversion of the sound trackimage to silver sulfide may be effectedat any stage in the process at which there is still silver in the image.In the case of the multi-layer film described in our prior point in theprocessing is after the blue-green development and'treatment in hypo atwhich point the nlm is dried. At this point the film contains images ofmetallic silver and blue-green dye in each of the layers as well as inthe upper layer of the sound track area. The vsound track may bebleached to halide or other salts of silver, such as silverferrocyanide, by means of an applicator rollers or other deviceaffecting the sound track portion only. The sound track image is thenconverted to silver sulfide which is not affected by succeeding steps inthe color development process. It is immaterial whether or not theblue-green dye image remains with the sound track silver sulde, assubsequent bleach baths will remove it.

The bleached silver halide sound track image may be converted to silversulde in anumber of ways. The lm may be washed and immersed indevelopable sulde solution which will cause l.

conversion of the sound track portion only to silver sulde. The film mayalso be treated with ammonia and hydrogen sulfide vapor to convert thesilver chloride-to silverA sulde. A further method oflocal sulding ofthe sound track area is to apply a sulfide solution by means of anapplicator roller or other suitable device to the sound track portion ofthe lm after it emerges, thoroughly squeegeed, from either of the twodifferential bleaches used for halogenizing the upper or upper twolayers in the dierential process described in our prior application,Serial No. 8,516.

In Fig. 1 of the accompanying drawing we have shown in diagrammatic formapparatus used in the preferred method of forming the silver sulfide'sound track, according to our invention. As shown therein the lm i0which contains images of metallic silver and blue-green dye in thelayers of the picture area and the upper layer of the sound track areais coated with water from the applicator portion il of the hopper i2.VThe water may contain a small amount of a suitable wetting agent, suchas saponin, to overcome the surface repellency oi the blue-green filmand a small amount of a moisture-retaining'agent, such as glycol orglycerin, in order to prevent drying out of the moistened stripsat theedges during the subsequent gas-treating process.

'After being moistened on the sound track porltion the film is passedthrough a slit into chamber H4 and over a roller into chamber l5 inwhich it is treated with chlorine or brnmine gas which enters thechamber by a pipe I6.

The lm then passes out of chamber i 5 and over another. roller into adrying chamber I3 in which it is washed free of bleaching gas by acurrent of air which enters the chamber i 3 by means oi. conduit I1 andleaves by meansof conduit I8. The humidity of the current of air passedthrough the chamber I3 must be carefully controlled to prevent drying ofthe moistened film. The current of air is for the purpose only ofremoving the chlorine or bromine bleaching gas.

'I'he lm is then passed over a third roller into the chamber I9 andthence into the chamber 20 where it is treated with ammonium sulfidevapor' or hydrogen sulde gas entering through pipe 2 I. After thistreatment the film passes over a fourth roller in chamber I9 and thenceout of the cham. ber. The sulding agent used in chamber 20 may also besupplied by bubbling air of amwhich a slight suction is maintained.Since both of the gases used in the toning are heavier than air, theyare retained in the toning vessels by gravity. Any air leaking into thesuction boxes i8 and I9 is immediately, swept up by ducts 22, the toninggases being lostr only to a small degree by being carried away assurface layers on the illm. Y

It is important to control the humidity during the entire gas toningoperation. If the humidity is'too low the moistened strip may becomeedgedried and if vthe humidity is too high, the picture area may bevisibly affected and objectionable surface deposits may be formed. Thegastoning operation should preferably be carried out at a temperature of60 F. or lower. The humidity should be between about 40% and about `60%.This humiditymust also be maintained suciently high in the dryingchamber i3 to prevent drying during the removal of the halogen gas. Thischamber is kept at a temperature of 50 to 60 F., and a relative humidityof between 40% and 60%.

Y It is also important to remove any traces of free sulfide from thetoned lm before the subsequent bleaching and color-forming developmentsteps of our process. The purpose of the bleaching step following therecording of the sound according to our preferred method is to transformthe silver images in certain layers of the picture area to silver halidewhich is developable. The presence` of any free sulfide in the bleachbath causes the silver image being bleached to be transformed to opaquesilver instead of to silver halide. Such contamination of the picturewith silver sulde would mean sacrificing picture quality in order` toobtain good sound quality.

The free sulfide is removed from the film by washing the film in chamber23 by a spray of water from pipe 2&1. 'Ihe water jets are preferablydirected obliquely across the lm from the picture area toward the soundtrack. This washing is followed by squeegeeing the film as shown at 25after which it passes through a drying chamber 25, in which it isthoroughly dried, preferably by the use of warm air. The lm may also betreated with chlorine or bromine gas or with a solution of chlorine orbromine, to oxidize any unused suliide on the film.

A second method for sulfiding the sound track employs the application ofa liquid bath containing a soluble sulfide. The bath employs a quinonebleaching agent and hydrochloric acid and converts the sound track tosilver sulfide in a single operation. The liquid -sulflding bath may beapplied by applicator II in the same manner as the water of the gastoning method. A suitable liquid sulfide bath may have the foll lowingcomposition:

The sodium sulfide used in ythis formula may vary from a few tenths of1% to about 3% or more of the amount of solution by weight.

Glycerin grams Hydrochloric acid grams-- 20 Y Quinone s. grams-- 5Sodium sulde grams-- 35 `Water liter l In this method of sulnding anafter-treatment is also necessary to oxidize or remove unused sulfide.This may be done by treating with chlorine or bromine gas as describedabove, or by strip application of a chlorine or bromine solution.

In Fig. 2 of the drawing we have shown the series of steps of formingthe silveri sulfide sound track as represented by successive sectionalviews of the iilxn. As shown therein 21 represents a multi-layer iilmhaving a transparent base. The sound track portion of the iilm isexposed through a mask 2l which prevents exposure of the picture area,the sound being recorded by a suitable recording device, the objectiveof which is represented at 29. The sound track may be recorded before orafter exposure of the picture area of the iilm.

After development the sound track area of the film appears as an image30 inthe upper layer of the film and a iogged image 3| in the two lowerlayers of the iilm. It is assumed that the sound track is formed in afllm being processed according to the reversal method and that the lowertwo layers have been fogged by one of the methods described above.

After bleaching, re-exposure and development of the film in the usualway as performed in the reversal method, the sound track appears ascomplementary image 32, the fogged image in the lower layers beingremoved by this treatment. After suliiding by one of the methodsdescribed above, the sound track appears as silver sulfideas shown at33. The film is then ready for the remaining processing steps to i'ormcolored images in the picture area.

Fig. 3 shows in enlarged form the applicator roller il used to apply thewater or suliiding solution to the film I0. 'The liquid applied to thesound track in this way is represented at 34.

'I'he sound track formed of silver sulfide according to our method has anumber of advantages. It is easy to form by a suliiding method such asthose described above, it is opaque to the photo-electric cell used insound reproducing, and it is not aiiected by successive processing stepsof bleaching and color development according to our preferred method offorming colored images. We are aware that photographic sound records ofsilver sulfide have been described hitherto, for example, by J. G.Capstai in U. S. Patent No. 1,973,463, granted September 11, 1934.Disclosures of this type do not, however, suggest a solution of thepresent problem, in which it is desired to form a sound track in a iilmwhich may contain latent picture images in adjacent layers and whichwill not require some special treatment, such as varnishing, to preventits destruction by subsequent steps of our process employing bleachbaths and colorforming developing operations.

Our method is susceptible of numerous modications and is to be limitedonly by the scope of the appended claims.

What we claim is:

1. The method of forming sound and naturalcolor picture images in a filmhaving a plurality of layers sensitive to different spectral regions onone side of a transparent support, which consists in forming positiveimages of metallic silver in bcthsound and picture areas, convertingonly the silver sound image to silver sulfide, and then successivelysubjecting the film to a series of bleaching and coloring steps tosuccessively convert different of the picture images to images of silverand a different dye, the bleaching step being one which affects metallicsilver but not silver sulfide and converts the picture image todevelopable salts, and the coloring step being a color-formingdevelopment in which a colorforming compound couples with theoxidization product of the developer and in which the silver sulfidesound image is not affected.

2. The method of forming sound and naturalcolor picture images in afilmY having a plurality of layers sensitive to different spectralregions onv one side of a transparent support, which consists in formingimages of metallic silver in rboth sound and picture areas, the soundimage being formed only in an upper layer of the film and the lowerlayers being fogged, subjecting the lm to a reversal development toproduce complementary silver and dye images in the picture area and thesound area of the upper layer, and clearing the sound area of the lowerlayers, converting only the sound image to silver suliide, and thensuccessively subjecting the iilm LEOPOLD D. MANNES. LEOPOLD GODOWSKY,JR.

